EP3741293B1 - Method and system for measuring blood flow - Google Patents
Method and system for measuring blood flow Download PDFInfo
- Publication number
- EP3741293B1 EP3741293B1 EP19176395.2A EP19176395A EP3741293B1 EP 3741293 B1 EP3741293 B1 EP 3741293B1 EP 19176395 A EP19176395 A EP 19176395A EP 3741293 B1 EP3741293 B1 EP 3741293B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- antennae
- magnetic field
- magnetic resonance
- signal
- designed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000000034 method Methods 0.000 title claims description 35
- 230000017531 blood circulation Effects 0.000 title claims description 21
- 230000033001 locomotion Effects 0.000 claims description 44
- 238000002595 magnetic resonance imaging Methods 0.000 claims description 34
- 230000004044 response Effects 0.000 claims description 33
- 238000005259 measurement Methods 0.000 claims description 29
- 238000000926 separation method Methods 0.000 claims description 13
- 230000004907 flux Effects 0.000 claims description 9
- 230000000241 respiratory effect Effects 0.000 claims description 9
- 230000000747 cardiac effect Effects 0.000 claims description 8
- 238000004590 computer program Methods 0.000 claims description 8
- 238000012880 independent component analysis Methods 0.000 claims description 8
- 238000004422 calculation algorithm Methods 0.000 claims description 2
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims description 2
- 238000010801 machine learning Methods 0.000 claims description 2
- 210000004204 blood vessel Anatomy 0.000 description 11
- 239000008280 blood Substances 0.000 description 9
- 210000004369 blood Anatomy 0.000 description 9
- 238000001208 nuclear magnetic resonance pulse sequence Methods 0.000 description 8
- 230000005540 biological transmission Effects 0.000 description 7
- 238000003384 imaging method Methods 0.000 description 7
- 238000003325 tomography Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 4
- 230000005284 excitation Effects 0.000 description 4
- 210000000709 aorta Anatomy 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 3
- 230000003387 muscular Effects 0.000 description 3
- 238000005086 pumping Methods 0.000 description 3
- 238000002583 angiography Methods 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000007175 bidirectional communication Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000013016 damping Methods 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 210000004072 lung Anatomy 0.000 description 2
- 210000000056 organ Anatomy 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000029058 respiratory gaseous exchange Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000002059 diagnostic imaging Methods 0.000 description 1
- 230000005281 excited state Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 239000011553 magnetic fluid Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 210000003205 muscle Anatomy 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000010363 phase shift Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000012549 training Methods 0.000 description 1
Images
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/026—Measuring blood flow
- A61B5/0263—Measuring blood flow using NMR
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/026—Measuring blood flow
- A61B5/0265—Measuring blood flow using electromagnetic means, e.g. electromagnetic flowmeter
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0033—Features or image-related aspects of imaging apparatus classified in A61B5/00, e.g. for MRI, optical tomography or impedance tomography apparatus; arrangements of imaging apparatus in a room
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7203—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal
- A61B5/7207—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal of noise induced by motion artifacts
- A61B5/7214—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal of noise induced by motion artifacts using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7228—Signal modulation applied to the input signal sent to patient or subject; demodulation to recover the physiological signal
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
- G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
- G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
- G01R33/563—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution of moving material, e.g. flow contrast angiography
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
- G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
- G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
- G01R33/563—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution of moving material, e.g. flow contrast angiography
- G01R33/56308—Characterization of motion or flow; Dynamic imaging
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
- A61B2562/02—Details of sensors specially adapted for in-vivo measurements
- A61B2562/0223—Magnetic field sensors
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
- A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb
- A61B5/113—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb occurring during breathing
Definitions
- the invention describes a method and a system for measuring blood flow, especially for a magnetic resonance imaging system ("MRI system").
- MRI system magnetic resonance imaging system
- MRI systems are used in medical examinations for recording (imaging) data of an examination object by exciting its nuclear spins that are aligned within a strong basic magnetic field.
- the precession or relaxation of the spins from this excited state into a state with less energy generates, as a response, a magnetic alternating field (radio frequency signal, "RF signal”) that is received via RF antennae.
- RF signal radio frequency signal
- the measurement of the MRI system requires a number of milliseconds up to seconds. While a longer recording time usually results in minimal noise artifacts, the influence of motion artifacts increases with the duration of the measurement.
- German patent application 10 2015 203 385 A1 describes a basic method of capturing the movements using a high-frequency signal.
- the signal is permanently captured in a patient recording of a magnetic resonance tomography system, and signal changes due to movements (e.g., due to changing interferences or damping) are evaluated.
- a movement of the patient caused by breathing or heartbeat may then be identified from certain patterns of this signal.
- German patent application 10 2015 224 158 A1 discloses a special transmitter for pilot tone navigation in a magnetic resonance tomography system.
- This pilot tone navigator includes a power supply and an antenna.
- the transmitter is configured to emit a pilot tone signal in the form of an electromagnetic alternating field by way of the antenna.
- the transmitter includes a decoupling element that decouples the transmitter output of signals that the antenna in a magnetic resonance tomography system receives by excitation pulses of the magnetic resonance tomography system.
- German patent application 10 2015 224 158 A1 further discloses a method of identifying a movement of a patient using a magnetic resonance tomography system with such transmitter that is arranged in close proximity to the heart or the lungs of the patient (e.g., on a body surface of the patient at a minimal distance from the organs). Then, the transmitter transmits the pilot tone signal and the magnetic resonance tomography system receives the pilot tone signal with one or a number of antennae and receivers that are typically provided to receive a magnetic resonance signal.
- N-MRA non-contrast MR angiography
- the unknown time delay between contraction of the heart and arrival of the pulse wave in the imaging volume is up to now either estimated based on length measurements or trial scans, or free-running sequences are used to measure continuously.
- a method according to the invention can be used for measuring blood flow.
- This blood flow could typically be the blood flow in an object of a patient, wherein the object is typically a blood vessel, but could also be regarded as an organ comprising blood vessels or another cavity where blood may flow (also a wound).
- the patient is preferably positioned in a magnetic resonance imaging system.
- the method comprises the following steps:
- a system for measuring blood flow is preferably designed to perform a method according to the invention and comprises the following components:
- the whole setup with the system comprising the generator coil RF reception system could be designated as "Pilot Tone navigator system” since it uses a pilot "tone” (the modulated magnetic field) for measurements.
- Changes in the electromagnetic environment within the examination volume e.g. by blood flow, respiratory motion, cardiac motion or further muscular or bowel movements, alter the generated modulated magnetic field.
- the generative field is set to a frequency just outside the imaging bandwidth around the Larmor frequency, the modulated magnetic field can easily be detected by the RF antennae.
- the generator coil may comprise a transmitter for pilot tone navigation in a magnetic resonance tomography system.
- the generator coil generates a modulated magnetic field with a first frequency band.
- an excitation signal is generated by an RF transmission antenna system of a magnetic resonance imaging system to generate a magnetic resonance signal with a second frequency band from the object.
- the second frequency band is at least essentially outside the first frequency band.
- the least two RF antennae of the RF reception system is configured to receive a frequency band that includes the first frequency band and the second frequency band.
- the modulated magnetic field induces eddy currents in the flowing blood, which in turn generates a magnetic field opposing the inducing field.
- an additional current is induced due to this motion. This changes the local magnetic environment and the response would differ from the original "tone", i.e. the original modulation of the initial magnetic field.
- the flow component can be separated from those induced from cardiac and respiratory motion or bowel/muscular movements using appropriate blind and/or semi-blind source separation methods such as e.g. Independent Component Analysis (ICA) or training with ground truth data.
- ICA Independent Component Analysis
- the control device may comprise additional units or devices for controlling components of a magnetic resonance imaging system, e.g. a sequence control unit for measurement sequence control, a memory, an RF transmission device that generates, amplifies, and transmits RF pulses, a gradient system interface, an RF reception device to acquire magnetic resonance signals and/or a reconstruction unit to reconstruct magnetic resonance image data.
- a magnetic resonance imaging system comprises a control device according to the invention or is at least designed to perform a method according to the invention.
- Some units or modules of the system or the control device mentioned above can be completely or partially realized as software modules running on a processor of a system or a control device.
- a realization largely in the form of software modules can have the advantage that applications already installed on an existing system can be updated, with relatively little effort, to install and run these units of the present application.
- the object of the invention is also achieved by a computer program product with a computer program that is directly loadable into the memory of a device of a system or a control device of a magnetic resonance imaging system, and which comprises program units to perform the steps of the inventive method when the program is executed by the control device or the system.
- such a computer program product can also comprise further parts such as documentation and/or additional components, also hardware components such as a hardware key (dongle etc.) to facilitate access to the software.
- a computer readable medium such as a memory stick, a hard-disk or other transportable or permanently-installed carrier can serve to transport and/or to store the executable parts of the computer program product so that these can be read by a processor unit of a control device, an MPSU or a system.
- a processor unit can comprise one or more microprocessors or their equivalents.
- the generator coil is embedded in a magnetic resonance scanner of a magnetic resonance imaging system, preferably near or in an RF reception antenna system (with one or more RF antennae) of the magnetic resonance scanner. It is preferred that the generator coil is positioned adjacent the examination space or in a unit that is placed at, under or on a patient for examination, e.g. in a local coil setup, since the nearer the generator coil is positioned to the patient the greater the excitation of the desired area with the modulated magnetic field. It is preferred that a number of coils used for imaging in a magnetic resonance scanner are used as generator coils.
- the RF reception system used for recording the response signals of the modulated magnetic field is the RF reception system of a magnetic resonance imaging system, wherein preferably the response signals of the modulated magnetic field are recorded by RF antennae from the RF reception antenna system of the magnetic resonance scanner.
- the, or at least one, (dominant) frequency of the modulation of the magnetic field lies within the normal bandwidth of the RF reception antenna system of the magnetic resonance scanner (e.g. in the order of some ten or hundred MHz).
- the frequency is dependent of the field strength, e.g. at a basic magnetic field of 7 T the frequency could be close to 300 MHz, at field strength below 0.5 T the frequency could be lower than 20 MHz.
- the frequency could be especially over 22 MHz and/or lower than 150 MHz.
- the frequency used for modulation may be between 57 MHz and 61 MHz or 64 MHz and 68 MHz. It is preferred that more than three RF antennae are used for measurement, since the more antennae are used the better the separation of the response signals can be performed.
- the frequency f used for modulation at a present magnetic field B is below 42 ⁇ B MHz/T and above 43 ⁇ B MHz/T, however, It is particularly preferred that the frequency f used for modulation at a present magnetic field B is above 38 ⁇ B MHz/T (if lower than the Larmor frequency) or below 47 ⁇ B MHz/T (if higher than the Larmor frequency).
- the separation of the flow component of the recorded signals from those signal components resulting from movements of the object is achieved by using (appropriate) blind and/or semi-blind source separation methods, preferably by using Independent Component Analysis (ICA) or by a machine learning algorithm trained with ground truth data.
- ICA Independent Component Analysis
- ICA Independent Component Analysis
- the object is arranged between the generator coil and the RF antennae, wherein at least the signals from the two RF antennae of the RF reception system that are positioned closest to a line parallel to the blood flow intended to be measured is recorded.
- the appropriate antennae e.g. coils of a magnetic resonance scanner
- the object is between the generator coil and the RF antennae, since there can be also recorded a useful response signal if an antenna array is used with an integrated generator coil.
- the magnetic field emitted by the object can be measured all around the object. This means, the response signals of the modulated magnetic field can be measured at an arbitrary position around the object and not only at a position opposite the generator coil.
- a modulation of the modulated magnetic field includes a frequency within a frequency range near the Larmor frequency of the hydrogen atoms of the object in an applied magnetic field, preferably within a variance of less than 10 percent deviating from this Larmor frequency.
- a modulation of the modulated magnetic field includes a frequency that is within the receiving frequency bandwidth of the RF antennae used for the measurement, preferably within a frequency range of less than 10 percent deviating from the Eigenfrequency of these RF antennae.
- parameters of the flow are computed, preferably a value of a flux and/or a periodicity.
- a preferred computing unit designed to compute parameters of the measured flow, preferably a value of a flux and/or a periodicity.
- the periodicity can be derived from the shape of the recorded signal over time
- the flux can be derived from the delay of recorded signals from different RF antennae.
- a preferred system comprises a generator coil designed to generate a modulated magnetic field, wherein the generator coil is preferably positioned inside a magnetic resonance scanner. Additionally, the system preferably comprises a generator unit for producing the modulation signal for the modulated magnetic field.
- the generator coil is preferably dumbbell-shaped, e.g. with two circular-shaped parts and an elongated part between these circular-shaped parts.
- the circular-shaped parts may be small relative to the wavelength of the modulated magnetic field, wherein the parts have preferably a diameter between 5 mm and 10 mm and the elongated part a length between 10 mm and 50 mm.
- the maximum field strength of the modulated magnetic field lies in the region of mT and is typically below 100 mT and above 1 mT. Especially when receiving units of an MR scanner are used, this field strength should be adjusted such that the received signal level is in the region of the signal levels received at normal MR imaging so that there is no overdrive of the electronics.
- a preferred system comprises an RF reception system with at least two RF antennae designed to record response signals of the modulated magnetic field from the object, wherein at least the response signals are measured by the RF antennae.
- the RF antennae are preferably an RF reception antenna system of a magnetic resonance imaging system.
- FIG. 1 shows a schematic representation of a magnetic resonance imaging system 1 ("MRI system").
- the MRI system 1 includes the actual magnetic resonance scanner (data acquisition unit) 2 with an examination space 3 or patient tunnel in which a patient or test person is positioned on a driven bed 8, in whose body the actual examination object is located.
- the magnetic resonance scanner 2 is typically equipped with a basic field magnet system 4, a gradient system 6, as well as an RF transmission antenna system 5, and an RF reception antenna system 7.
- the RF transmission antenna system 5 is a whole-body coil permanently installed in the magnetic resonance scanner 2, in contrast to which the RF reception antenna system 7 is formed as a plurality of local coils to be arranged on the patient or test subject.
- the whole-body coil can also be used as an RF reception antenna system, and the local coils can respectively be switched into different operating modes.
- the RF reception antenna system 7 is used as RF antennae 21 according to the invention.
- a generator coil 20 is located below the object.
- the RF antennae 21 could be at the position of the whole-body coil (or the whole-body coil can be used if it comprises more than one single coil), and the local coil 7 could be used as generator coil 20.
- the basic field magnet system 4 is designed such that a region of Interest ("RoI”) can be recorded.
- RoI region of Interest
- the gradient system 6 typically includes individually controllable gradient coils in order to be able to switch (activate) gradients in the x-direction, y-direction or z-direction independently of one another.
- the MRI system 1 shown here is a whole-body system with a patient tunnel into which a patient can be completely introduced.
- the invention can also be used at other MRI systems, for example with a laterally open, C-shaped housing, as well as in smaller magnetic resonance scanners in which only one body part can be positioned.
- the MRI system 1 has a central control device 13 that is used to control the MRI system 1.
- This central control device 13 includes a sequence control unit 14 for measurement sequence control.
- the sequence control unit 14 the series of radio frequency pulses ("RF pulses") and gradient pulses can be controlled depending on a selected pulse sequence or, respectively, a series of multiple pulse sequences to acquire magnetic resonance images of the RoI within a measurement session.
- RF pulses radio frequency pulses
- gradient pulses can be controlled depending on a selected pulse sequence or, respectively, a series of multiple pulse sequences to acquire magnetic resonance images of the RoI within a measurement session.
- RF pulses radio frequency pulses
- gradient pulses can be controlled depending on a selected pulse sequence or, respectively, a series of multiple pulse sequences to acquire magnetic resonance images of the RoI within a measurement session.
- RF pulses radio frequency pulses
- gradient pulses can be controlled depending on a selected pulse sequence or, respectively, a series of multiple pulse sequences to acquire magnetic resonance images of the RoI within a
- the central control device 13 To output the individual RF pulses of a pulse sequence, the central control device 13 has an RF transmission device 15 that generates and amplifies the RF pulses and feeds them into the RF transmission antenna system 5 via a suitable interface (not shown in detail). To control the gradient coils of the gradient system 6, the control device 13 has a gradient system interface 16. The sequence control unit 14 communicates in a suitable manner with the RF transmission device 15 and the gradient system interface 16 to emit the pulse sequence.
- control device 13 has an RF reception device 17 (likewise communicating with the sequence control unit 14 in a suitable manner) in order to acquire magnetic resonance signals (i.e. raw data) for the individual measurements, by which magnetic resonance signals are received in a coordinated manner from the RF reception antenna system 7 within the scope of the pulse sequence.
- RF reception device 17 likewise communicating with the sequence control unit 14 in a suitable manner
- a reconstruction unit 18 receives the acquired raw data and reconstructs magnetic resonance image data therefrom for the measurements. This reconstruction is typically performed on the basis of parameters that may be specified in the respective measurement or control protocol. For example, the image data can then be stored in a memory 19.
- Operation of the central control device 13 can take place via a terminal 11 with an input unit 10 and a display unit 9, via which the entire MRI system 1 can thus also be operated by an operator.
- MR images can also be displayed at the display unit 9, and measurements can be planned and started by means of the input unit (possibly in combination with the display unit 9), and in particular suitable control protocols can be selected (and possibly modified) with suitable series of pulse sequences as explained above.
- the control device 13 comprises a system 12 designed to perform the method according to the invention.
- This system 12 comprises the following components that may partly appear to be software modules.
- the system comprises: A first data-interface 22 designed for sending a signal to a generator coil 20, wherein this signal is designed to generate a (low-power) modulated magnetic field in the generator coil 20.
- the signal can be produced by a generator unit 25. Since the recording RF antennae have an Eigenfrequency in the range of MHz, the signal should be a periodic MHz-signal.
- a second data-interface 22 designed for recording response signals of the modulated magnetic field from the object measured with an RF reception system, wherein at least the response signals are measured by two RF antennae of the RF reception system.
- the first and second data interface are one single data interface designed for bi-directional communication.
- a separation unit 23 designed to separate a flow component of the recorded signals from those signal components resulting from cardiac and respiratory motion. Since the measured signals can easily be turned into digital values by an analog-digital-discriminator, the separation could be performed by calculating steps, e.g. by a calculation based on an Independent Component Analysis.
- a computing unit 24 that is designed to compute parameters of the measured flow.
- a value for the flux (blood volume per second) and the periodicity of the blood flow is calculated based on the separated data.
- the flux may be determined from the phase shift between the signals of two (or more) antennae, the volume of flowing blood by the amplitude of a signal.
- the generator coil 20 is part of the magnetic resonance scanner 2. However, it could also be regarded as a part of the system 12. The same is valid for the RF antennae 21.
- the local coils 7 of the magnetic resonance scanner 2 are used as RF antennae 21.
- the RF antennae 21 could be regarded as a part of the system 12.
- the MRI system 1 according to the invention, and in particular the control device 13, can have a number of additional components that are not shown in detail here but are typically present in such systems, for example a network interface in order to connect the entire system with a network and be able to exchange raw data and/or image data or, respectively, parameter maps, but also additional data (for example patient-relevant data or control protocols).
- additional components for example a network interface in order to connect the entire system with a network and be able to exchange raw data and/or image data or, respectively, parameter maps, but also additional data (for example patient-relevant data or control protocols).
- Figure 2 shows a block diagram of the process flow of a preferred method according to the invention
- a modulated magnetic field is generated by a generator coil.
- the modulation could be following an alternating signal.
- the frequency of the modulation of the magnetic field is given with the field-strength of the predefined basic magnetic field. This field-strength defines the Larmor frequency that is measured during medical imaging wherein the Eigenfrequency of the RF reception antenna system 7 is designed to meet the Larmor frequency.
- the frequency of the modulation should be higher or lower than the Larmor frequency but lie within the bandwidth of the RF reception antenna system 7. In this example, the frequency of the modulation may be between 22 MHz and 125 MHz. However, depending on the magnetic field, the frequency may be higher or lower.
- the generating coil 20 is positioned near the object O. This has the advantage that the modulated magnetic field is generated near the region of interest, since the field-strength of the modulated magnetic field decreases with increasing distance d with approximately 1/d 3 (Biot-Savart law) .
- step II response signals of the modulated magnetic field from the object are recorded with an RF reception system, e.g. as shown in Figure 1 the local coil 7.
- the response signals should be measured by at least two RF antennae of the RF reception system.
- the modulated magnetic field applied in step I induces eddy currents in the blood which is a conductive fluid. These eddy currents in turn generate a magnetic field opposing the generated field.
- an additional current is induced due to motion and the local magnetic environment is changed. This can be recorded by the RF antennae.
- step III the flow component of the recorded signals is separated from those signal components resulting from movements of the object, such as cardiac and respiratory motion. Due to the pumping action of the heart, the signals from the blood flow can be identified and separated from other contributions to the signal by regarding the shape and/or other (statistical) parameters (as e.g. frequency or shape of the distribution) of the signal. For separation from contributions from cardiac and respiratory motion, appropriate blind and/or semi-blind source separation methods can be used such as e.g. ICA.
- step IV parameters of the blood flow are computed, such as a value of the flux and/or the periodicity of the flow.
- FIG 3 shows an example of an arrangement of the coils. Unlike figure 1 , where a local coil 7 was used as RF antenna 21, it is now used as generator coil 20 sending a modulated magnetic field M with a frequency of about 50 MHz to the heart of a patient.
- the generator coil 20 may be dumbbell-shaped as shown in the dashed example.
- the movement of the heart should be measured as well as the flow in the Aorta.
- RF antennae 21 which could be part of the RF reception antenna system 7, measure the response of the modulated magnetic field after it has passed heart and aorta.
- additional antennae may be used, too, e.g. RF antennae in the body array, since the response signal is emitted by the object in all directions.
- the signals recorded with the RF antennae 21 could then be processed in that the movement of the heart is separated from the contribution of the blood flow in the aorta as already explained above.
- FIG. 4 outlines an example for a possible measurement without a flow.
- a blood vessel B lies between a generator coil 21 on one side and two RF antennae 20 on the other side.
- the RF antenna 20 emits a modulated magnetic field M that is created in a generator unit 25 with a frequency in the order of some ten to some hundred MHz, depending on field-strength.
- the RF antennae 21 measure the modulated magnetic field M passing through the blood vessel B and an RF reception device 17 at each RF antenna forms a measuring signal or measurement data.
- the measured signal of each RF antenna 21 is shown adjacent the respective RF antenna 21. Since there is no flow in the blood vessel B in this figure, the signals are almost identical (here due to the symmetric setup of the RF antennae 21).
- the generator coil may e.g. also lie between the blood vessel and the RF antennae, since it is not necessary that the blood vessel lies between the generator coil and the RF antennae.
- Figure 5 outlines an example for a possible measurement with a flow.
- the same setup is used as in figure 4 .
- there is now blood flowing through the blood vessel B causing the magnetic field to slightly deform in comparison to figure 4 .
- the measured signals of the RF antennae 21, again shown adjacent the respective RF antenna 21 are different.
- This difference offers on the one hand a possibility to separate the contribution of the blood flow from contribution of other measurements (that may e.g. form an identical offset in both measurements) and on the other hand a possibility to calculate parameters of the flow itself (e.g. the flux or the periodicity).
- Figure 6 shows an example of a flow-measurement, e.g. recorded with the setup of figure 5 .
- the amplitude of the measured signals S1, S2 is drawn against the time t in arbitrary units (e.g. mV).
- the difference between the amplitudes of the two signals S1, S2 results from different energy input in the RF antennae 21 (see e.g. the different field strength in figure 5 at the position of the RF antennae 21).
- the output of the RF antennae 21 depends on their position relative to the generator coil 20 and the flow direction.
- the heartbeat modulates the signals S1, S2 so that the pulse frequency of the blood vessel B can be determined.
- the signal in the second coil is delayed which can be seen by comparing the two points in time t1, t2 pointing to respective peaks of the blood flow.
- the delay may e.g. be approximately 120ms. Since the position of the RF antennae 21 is well-known, this delay can be used to calculate further parameters as e.g. the velocity of the flow.
Landscapes
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Health & Medical Sciences (AREA)
- Molecular Biology (AREA)
- Public Health (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Veterinary Medicine (AREA)
- Biophysics (AREA)
- Pathology (AREA)
- Biomedical Technology (AREA)
- Heart & Thoracic Surgery (AREA)
- Medical Informatics (AREA)
- Animal Behavior & Ethology (AREA)
- Surgery (AREA)
- Signal Processing (AREA)
- Physiology (AREA)
- Radiology & Medical Imaging (AREA)
- Vascular Medicine (AREA)
- Computer Vision & Pattern Recognition (AREA)
- Psychiatry (AREA)
- Artificial Intelligence (AREA)
- High Energy & Nuclear Physics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Hematology (AREA)
- Cardiology (AREA)
- Electromagnetism (AREA)
- Magnetic Resonance Imaging Apparatus (AREA)
Description
- The invention describes a method and a system for measuring blood flow, especially for a magnetic resonance imaging system ("MRI system").
- MRI systems are used in medical examinations for recording (imaging) data of an examination object by exciting its nuclear spins that are aligned within a strong basic magnetic field. The precession or relaxation of the spins from this excited state into a state with less energy generates, as a response, a magnetic alternating field (radio frequency signal, "RF signal") that is received via RF antennae. The RF frequency strongly depends on the basic magnetic field.
- Depending on the pulse sequence used for recording, the measurement of the MRI system requires a number of milliseconds up to seconds. While a longer recording time usually results in minimal noise artifacts, the influence of motion artifacts increases with the duration of the measurement.
- Although most patients try to remain still, in order to avoid motion artifacts, there are unavoidable movements of the patient that cannot be stopped, such as e.g. breathing or heartbeat.
- It is state of the art to measure the movements of a patient by using mechanical sensors or electrodes that measure the excitation potential of the muscles.
-
German patent application 10 2015 203 385 A1 -
German patent application 10 2015 224 158 A1 -
German patent application 10 2015 224 158 A1 - Although it is possible to measure the motion of the heart or of the lungs, no non-invasive sensor currently exists that is capable of continuously detecting flow within a magnetic resonance ("MR") scanner environment. This is very disadvantageous, since the accurate detection of blood flow is an important factor in non-contrast MR angiography (NC-MRA) like NATIVE or QISS of extremities where the correct trigger time, i.e. the arrival of the pulse wave in the examination volume, is delayed with respect to the ECG R-peak by an unknown time.
- The unknown time delay between contraction of the heart and arrival of the pulse wave in the imaging volume is up to now either estimated based on length measurements or trial scans, or free-running sequences are used to measure continuously.
- Currently existing magnetic flowmeters for blood flow use electrodes attached to the skin to measure induced potentials due to motion
US-2015/272453-A1 ,US-2015/241538-A1 andUS-2018/055380-A1 show MRI angiography systems.WO-2019/096707-A1 ,EP-3413076-A1 ,US-2010/106008-A1 ,US-2018/353139-A1 , andUS-2017/160364-A1 show methods of motion detection in MRI systems. - It is the object of the present invention to improve the known systems, devices, and methods to facilitate an improvement for measurements of a blood flow of a patient, especially with a magnetic resonance imaging system.
- This object is achieved by a method according to claim 1, a system according to
claim 8, a control device according toclaim 12, and a magnetic resonance imaging system according toclaim 13. - A method according to the invention can be used for measuring blood flow. This blood flow could typically be the blood flow in an object of a patient, wherein the object is typically a blood vessel, but could also be regarded as an organ comprising blood vessels or another cavity where blood may flow (also a wound). The patient is preferably positioned in a magnetic resonance imaging system.
- The method comprises the following steps:
- Generating a (low-power) modulated magnetic field by a generator coil. This field should comprise at least one frequency that can be measured by an RF reception system. A simple modulated magnetic field could have the shape of a sine wave. However, it is also possible to have a more complex modulation comprising a multiplicity of sine waves, e.g. a rectangular modulation. Since it is very advantageous in magnetic resonance imaging to use the RF reception system of a magnetic resonance scanner, the frequency (or at least one dominant frequency) should accord to the receiving bandwidth of this RF reception system but deviate from the Larmor frequency recorded during regular data acquisition for imaging. It is clear that best results are achieved when the modulated magnetic field is sent directly to the object positioned for examination.
- Recording response signals of the modulated magnetic field from the object with the RF reception system, wherein the response signals are measured by at least two RF antennae of the RF reception system. These RF antennae are preferably coils, particularly preferably coils used for imaging in a magnetic resonance scanner, however, they could also have another shape (e.g. of a linear dipole).
- Separating a flow component of the recorded response signals from those signal components resulting from movements of the object. Such movements could include, besides muscular movements of the extremities, cardiac and respiratory motion or bowel movements. A movement-dependent change in the received signal can be identified and then separated by using signal analysis. For example, a flow movement may be detected by identifying a variation in the amplitude of the modulated magnetic field ("pilot tone signal"), caused by changes in the load of the RF antennae or the change in superimpositions or damping due to the blood flow in a blood vessel. The flow movement may be differentiated from other disturbing influences by the specific frequency and signal profile that is different from the frequency or signal profile of e.g. a respiratory movement or a heartbeat.
- A system for measuring blood flow is preferably designed to perform a method according to the invention and comprises the following components:
- A first data-interface designed for sending a signal to a generator coil, wherein this signal is designed to generate a (low-power) modulated magnetic field in the generator coil. This signal could be generated by a signal generator that can also be part of the system. However, the signal generator could also be part of an (external) generator coil, wherein the signal sent through the data interface could be a simple "on" signal to trigger the signal generator.
- A second data-interface designed for recording response signals of the modulated magnetic field from an object measured with an RF reception system, wherein at least the response signals are measured by two RF antennae of the RF reception system. The RF reception system could be part of the system and should comprise data acquisition units that are designed to modify the signals of the RF antennae, e.g. amplify and/or shape it, such that the system can use the signals for further processing. For example, the RF reception system can provide digital data of the recorded signals. It should be noted that the first and second data interface could be one single unit designed for bi-directional communication.
- A separation unit designed to separate a flow component of the recorded response signals from those signal components resulting from movements of the object.
- The whole setup with the system comprising the generator coil RF reception system could be designated as "Pilot Tone navigator system" since it uses a pilot "tone" (the modulated magnetic field) for measurements. Changes in the electromagnetic environment within the examination volume, e.g. by blood flow, respiratory motion, cardiac motion or further muscular or bowel movements, alter the generated modulated magnetic field. When the generative field is set to a frequency just outside the imaging bandwidth around the Larmor frequency, the modulated magnetic field can easily be detected by the RF antennae.
- The generator coil may comprise a transmitter for pilot tone navigation in a magnetic resonance tomography system. Preferably, the generator coil generates a modulated magnetic field with a first frequency band. Preferably, an excitation signal is generated by an RF transmission antenna system of a magnetic resonance imaging system to generate a magnetic resonance signal with a second frequency band from the object. Preferably, the second frequency band is at least essentially outside the first frequency band. Preferably, the least two RF antennae of the RF reception system is configured to receive a frequency band that includes the first frequency band and the second frequency band.
- Since blood is a (para)magnetic fluid, the modulated magnetic field induces eddy currents in the flowing blood, which in turn generates a magnetic field opposing the inducing field. Thus, when the blood moves due to the heart's pumping activity, an additional current is induced due to this motion. This changes the local magnetic environment and the response would differ from the original "tone", i.e. the original modulation of the initial magnetic field.
- Since the response is measured using a (e.g. relatively vast) number of RF antennae (e.g. receiver coils of an MR scanner), the flow component can be separated from those induced from cardiac and respiratory motion or bowel/muscular movements using appropriate blind and/or semi-blind source separation methods such as e.g. Independent Component Analysis (ICA) or training with ground truth data.
- A control device according to the invention for controlling a magnetic resonance imaging system comprises a system according to the invention and/or is designed to perform a method according to the invention. The control device may comprise additional units or devices for controlling components of a magnetic resonance imaging system, e.g. a sequence control unit for measurement sequence control, a memory, an RF transmission device that generates, amplifies, and transmits RF pulses, a gradient system interface, an RF reception device to acquire magnetic resonance signals and/or a reconstruction unit to reconstruct magnetic resonance image data.
- A magnetic resonance imaging system according to the invention comprises a control device according to the invention or is at least designed to perform a method according to the invention.
- Some units or modules of the system or the control device mentioned above can be completely or partially realized as software modules running on a processor of a system or a control device. A realization largely in the form of software modules can have the advantage that applications already installed on an existing system can be updated, with relatively little effort, to install and run these units of the present application. The object of the invention is also achieved by a computer program product with a computer program that is directly loadable into the memory of a device of a system or a control device of a magnetic resonance imaging system, and which comprises program units to perform the steps of the inventive method when the program is executed by the control device or the system. In addition to the computer program, such a computer program product can also comprise further parts such as documentation and/or additional components, also hardware components such as a hardware key (dongle etc.) to facilitate access to the software.
- A computer readable medium such as a memory stick, a hard-disk or other transportable or permanently-installed carrier can serve to transport and/or to store the executable parts of the computer program product so that these can be read by a processor unit of a control device, an MPSU or a system. A processor unit can comprise one or more microprocessors or their equivalents.
- Particularly advantageous embodiments and features of the invention are given by the dependent claims, as revealed in the following description. Features of different claim categories may be combined as appropriate to give further embodiments not described herein.
- According to a preferred method, the generator coil is embedded in a magnetic resonance scanner of a magnetic resonance imaging system, preferably near or in an RF reception antenna system (with one or more RF antennae) of the magnetic resonance scanner. It is preferred that the generator coil is positioned adjacent the examination space or in a unit that is placed at, under or on a patient for examination, e.g. in a local coil setup, since the nearer the generator coil is positioned to the patient the greater the excitation of the desired area with the modulated magnetic field. It is preferred that a number of coils used for imaging in a magnetic resonance scanner are used as generator coils.
- According to a preferred method, the RF reception system used for recording the response signals of the modulated magnetic field is the RF reception system of a magnetic resonance imaging system, wherein preferably the response signals of the modulated magnetic field are recorded by RF antennae from the RF reception antenna system of the magnetic resonance scanner. As stated above, it is preferred that the, or at least one, (dominant) frequency of the modulation of the magnetic field lies within the normal bandwidth of the RF reception antenna system of the magnetic resonance scanner (e.g. in the order of some ten or hundred MHz). The frequency is dependent of the field strength, e.g. at a basic magnetic field of 7 T the frequency could be close to 300 MHz, at field strength below 0.5 T the frequency could be lower than 20 MHz. At a basic magnetic field of 1.5 T the frequency could be especially over 22 MHz and/or lower than 150 MHz. For example, since the Larmor frequency at a basic magnetic field of 1.5 T is about 62.5 MHz, the frequency used for modulation may be between 57 MHz and 61 MHz or 64 MHz and 68 MHz. It is preferred that more than three RF antennae are used for measurement, since the more antennae are used the better the separation of the response signals can be performed.
- With the Larmor frequency for a proton with the gyromagnetic moment of 267,5 MHz/T, the Larmor frequency fL at a magnetic field B could be calculated from fL = 267,5/(2·π)·B MHz/T. Thus, the frequency f used for modulation at a present magnetic field B should be around (but especially not equal) fL = 42,58·B MHz/T. It is preferred that the frequency f used for modulation at a present magnetic field B is below 42·B MHz/T and above 43·B MHz/T, however, It is particularly preferred that the frequency f used for modulation at a present magnetic field B is above 38·B MHz/T (if lower than the Larmor frequency) or below 47·B MHz/T (if higher than the Larmor frequency).
- According to a preferred method, the separation of the flow component of the recorded signals from those signal components resulting from movements of the object, e.g. cardiac and respiratory motion, is achieved by using (appropriate) blind and/or semi-blind source separation methods, preferably by using Independent Component Analysis (ICA) or by a machine learning algorithm trained with ground truth data. These methods for separation of signal contributions are well-known. It is also preferred to record a (image) navigator during a reference scan and then determine a combination that provides a norm (e.g. L2) that minimizes the difference between the navigator and the recorded signal (of the response signal or of the flow component).
- According to a preferred method, the object is arranged between the generator coil and the RF antennae, wherein at least the signals from the two RF antennae of the RF reception system that are positioned closest to a line parallel to the blood flow intended to be measured is recorded. Since the course of blood vessels in a body is known and the region of interest is known, the appropriate antennae (e.g. coils of a magnetic resonance scanner) can be selected accordingly. Alternatively, it is also possible to arrange antennae appropriately.
- It should be noted that it is not necessary for the invention that the object is between the generator coil and the RF antennae, since there can be also recorded a useful response signal if an antenna array is used with an integrated generator coil. The magnetic field emitted by the object can be measured all around the object. This means, the response signals of the modulated magnetic field can be measured at an arbitrary position around the object and not only at a position opposite the generator coil.
- According to a preferred method, a modulation of the modulated magnetic field includes a frequency within a frequency range near the Larmor frequency of the hydrogen atoms of the object in an applied magnetic field, preferably within a variance of less than 10 percent deviating from this Larmor frequency.
- Alternatively or additionally, a modulation of the modulated magnetic field includes a frequency that is within the receiving frequency bandwidth of the RF antennae used for the measurement, preferably within a frequency range of less than 10 percent deviating from the Eigenfrequency of these RF antennae.
- According to a preferred method, after separating the flow component of the recorded signals from those signal components resulting from movements of the object, parameters of the flow are computed, preferably a value of a flux and/or a periodicity. This could be achieved with a preferred computing unit designed to compute parameters of the measured flow, preferably a value of a flux and/or a periodicity. For example, the periodicity can be derived from the shape of the recorded signal over time, the flux can be derived from the delay of recorded signals from different RF antennae.
- A preferred system comprises a generator coil designed to generate a modulated magnetic field, wherein the generator coil is preferably positioned inside a magnetic resonance scanner. Additionally, the system preferably comprises a generator unit for producing the modulation signal for the modulated magnetic field.
- The generator coil is preferably dumbbell-shaped, e.g. with two circular-shaped parts and an elongated part between these circular-shaped parts. The circular-shaped parts may be small relative to the wavelength of the modulated magnetic field, wherein the parts have preferably a diameter between 5 mm and 10 mm and the elongated part a length between 10 mm and 50 mm. The maximum field strength of the modulated magnetic field lies in the region of mT and is typically below 100 mT and above 1 mT. Especially when receiving units of an MR scanner are used, this field strength should be adjusted such that the received signal level is in the region of the signal levels received at normal MR imaging so that there is no overdrive of the electronics.
- A preferred system comprises an RF reception system with at least two RF antennae designed to record response signals of the modulated magnetic field from the object, wherein at least the response signals are measured by the RF antennae. The RF antennae are preferably an RF reception antenna system of a magnetic resonance imaging system.
- Other objects and features of the present invention will become apparent from the following detailed descriptions considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention.
-
Figure 1 shows a simplified MRI system with an example for a system according to an embodiment of the invention. -
Figure 2 shows a block diagram of the process flow of a preferred method according to the invention. -
Figure 3 shows an example of an arrangement of the coils. -
Figure 4 outlines an example for a possible measurement without a flow. -
Figure 5 outlines an example for a possible measurement with a flow. -
Figure 6 shows an example of a flow-measurement. - In the diagrams, like numbers refer to like objects throughout. Objects in the diagrams are not necessarily drawn to scale.
-
Figure 1 shows a schematic representation of a magnetic resonance imaging system 1 ("MRI system"). The MRI system 1 includes the actual magnetic resonance scanner (data acquisition unit) 2 with an examination space 3 or patient tunnel in which a patient or test person is positioned on a drivenbed 8, in whose body the actual examination object is located. - The magnetic resonance scanner 2 is typically equipped with a basic field magnet system 4, a gradient system 6, as well as an RF
transmission antenna system 5, and an RFreception antenna system 7. In the shown exemplary embodiment, the RFtransmission antenna system 5 is a whole-body coil permanently installed in the magnetic resonance scanner 2, in contrast to which the RFreception antenna system 7 is formed as a plurality of local coils to be arranged on the patient or test subject. In principle, however, the whole-body coil can also be used as an RF reception antenna system, and the local coils can respectively be switched into different operating modes. - In this example, the RF
reception antenna system 7 is used asRF antennae 21 according to the invention. Below the object, agenerator coil 20 is located. In another example, theRF antennae 21 could be at the position of the whole-body coil (or the whole-body coil can be used if it comprises more than one single coil), and thelocal coil 7 could be used asgenerator coil 20. - The basic field magnet system 4 is designed such that a region of Interest ("RoI") can be recorded. Here it is designed in a typical manner so that it generates a basic magnetic field in the longitudinal direction of the patient, i.e. along the longitudinal axis of the magnetic resonance scanner 2 that proceeds in the z-direction. The gradient system 6 typically includes individually controllable gradient coils in order to be able to switch (activate) gradients in the x-direction, y-direction or z-direction independently of one another.
- The MRI system 1 shown here is a whole-body system with a patient tunnel into which a patient can be completely introduced. However, in principle the invention can also be used at other MRI systems, for example with a laterally open, C-shaped housing, as well as in smaller magnetic resonance scanners in which only one body part can be positioned.
- Furthermore, the MRI system 1 has a
central control device 13 that is used to control the MRI system 1. Thiscentral control device 13 includes asequence control unit 14 for measurement sequence control. With thissequence control unit 14, the series of radio frequency pulses ("RF pulses") and gradient pulses can be controlled depending on a selected pulse sequence or, respectively, a series of multiple pulse sequences to acquire magnetic resonance images of the RoI within a measurement session. For example, such a series of pulse sequences can be predetermined within a measurement or control protocol P. Different control protocols P for different measurements or measurement sessions are typically stored in amemory 19 and can be selected by an operator (and possibly modified as necessary) and then be used to implement the measurement. - To output the individual RF pulses of a pulse sequence, the
central control device 13 has anRF transmission device 15 that generates and amplifies the RF pulses and feeds them into the RFtransmission antenna system 5 via a suitable interface (not shown in detail). To control the gradient coils of the gradient system 6, thecontrol device 13 has agradient system interface 16. Thesequence control unit 14 communicates in a suitable manner with theRF transmission device 15 and thegradient system interface 16 to emit the pulse sequence. - Moreover, the
control device 13 has an RF reception device 17 (likewise communicating with thesequence control unit 14 in a suitable manner) in order to acquire magnetic resonance signals (i.e. raw data) for the individual measurements, by which magnetic resonance signals are received in a coordinated manner from the RFreception antenna system 7 within the scope of the pulse sequence. - A
reconstruction unit 18 receives the acquired raw data and reconstructs magnetic resonance image data therefrom for the measurements. This reconstruction is typically performed on the basis of parameters that may be specified in the respective measurement or control protocol. For example, the image data can then be stored in amemory 19. - Operation of the
central control device 13 can take place via a terminal 11 with aninput unit 10 and adisplay unit 9, via which the entire MRI system 1 can thus also be operated by an operator. MR images can also be displayed at thedisplay unit 9, and measurements can be planned and started by means of the input unit (possibly in combination with the display unit 9), and in particular suitable control protocols can be selected (and possibly modified) with suitable series of pulse sequences as explained above. - The
control device 13 comprises asystem 12 designed to perform the method according to the invention. Thissystem 12 comprises the following components that may partly appear to be software modules. The system comprises:
A first data-interface 22 designed for sending a signal to agenerator coil 20, wherein this signal is designed to generate a (low-power) modulated magnetic field in thegenerator coil 20. The signal can be produced by agenerator unit 25. Since the recording RF antennae have an Eigenfrequency in the range of MHz, the signal should be a periodic MHz-signal. - A second data-
interface 22 designed for recording response signals of the modulated magnetic field from the object measured with an RF reception system, wherein at least the response signals are measured by two RF antennae of the RF reception system. Here the first and second data interface are one single data interface designed for bi-directional communication. - A
separation unit 23 designed to separate a flow component of the recorded signals from those signal components resulting from cardiac and respiratory motion. Since the measured signals can easily be turned into digital values by an analog-digital-discriminator, the separation could be performed by calculating steps, e.g. by a calculation based on an Independent Component Analysis. - A
computing unit 24 that is designed to compute parameters of the measured flow. Here a value for the flux (blood volume per second) and the periodicity of the blood flow is calculated based on the separated data. The flux may be determined from the phase shift between the signals of two (or more) antennae, the volume of flowing blood by the amplitude of a signal. - In this example, the
generator coil 20 is part of the magnetic resonance scanner 2. However, it could also be regarded as a part of thesystem 12. The same is valid for theRF antennae 21. Here thelocal coils 7 of the magnetic resonance scanner 2 are used asRF antennae 21. However, also theRF antennae 21 could be regarded as a part of thesystem 12. - The MRI system 1 according to the invention, and in particular the
control device 13, can have a number of additional components that are not shown in detail here but are typically present in such systems, for example a network interface in order to connect the entire system with a network and be able to exchange raw data and/or image data or, respectively, parameter maps, but also additional data (for example patient-relevant data or control protocols). -
Figure 2 shows a block diagram of the process flow of a preferred method according to the invention - In step I, a modulated magnetic field is generated by a generator coil. The modulation could be following an alternating signal. The frequency of the modulation of the magnetic field is given with the field-strength of the predefined basic magnetic field. This field-strength defines the Larmor frequency that is measured during medical imaging wherein the Eigenfrequency of the RF
reception antenna system 7 is designed to meet the Larmor frequency. The frequency of the modulation should be higher or lower than the Larmor frequency but lie within the bandwidth of the RFreception antenna system 7. In this example, the frequency of the modulation may be between 22 MHz and 125 MHz. However, depending on the magnetic field, the frequency may be higher or lower. - In
Figure 1 , the generatingcoil 20 is positioned near the object O. This has the advantage that the modulated magnetic field is generated near the region of interest, since the field-strength of the modulated magnetic field decreases with increasing distance d with approximately 1/d3 (Biot-Savart law) . - In step II, response signals of the modulated magnetic field from the object are recorded with an RF reception system, e.g. as shown in
Figure 1 thelocal coil 7. The response signals should be measured by at least two RF antennae of the RF reception system. - The modulated magnetic field applied in step I induces eddy currents in the blood which is a conductive fluid. These eddy currents in turn generate a magnetic field opposing the generated field. When the blood moves due to the heart's pumping activity an additional current is induced due to motion and the local magnetic environment is changed. This can be recorded by the RF antennae.
- In step III, the flow component of the recorded signals is separated from those signal components resulting from movements of the object, such as cardiac and respiratory motion. Due to the pumping action of the heart, the signals from the blood flow can be identified and separated from other contributions to the signal by regarding the shape and/or other (statistical) parameters (as e.g. frequency or shape of the distribution) of the signal. For separation from contributions from cardiac and respiratory motion, appropriate blind and/or semi-blind source separation methods can be used such as e.g. ICA.
- In step IV, parameters of the blood flow are computed, such as a value of the flux and/or the periodicity of the flow.
-
Figure 3 shows an example of an arrangement of the coils. Unlikefigure 1 , where alocal coil 7 was used asRF antenna 21, it is now used asgenerator coil 20 sending a modulated magnetic field M with a frequency of about 50 MHz to the heart of a patient. Thegenerator coil 20 may be dumbbell-shaped as shown in the dashed example. Here, the movement of the heart should be measured as well as the flow in the Aorta. -
Several RF antennae 21, which could be part of the RFreception antenna system 7, measure the response of the modulated magnetic field after it has passed heart and aorta. Here, additional antennae may be used, too, e.g. RF antennae in the body array, since the response signal is emitted by the object in all directions. - The signals recorded with the
RF antennae 21 could then be processed in that the movement of the heart is separated from the contribution of the blood flow in the aorta as already explained above. -
Figure 4 outlines an example for a possible measurement without a flow. A blood vessel B lies between agenerator coil 21 on one side and twoRF antennae 20 on the other side. TheRF antenna 20 emits a modulated magnetic field M that is created in agenerator unit 25 with a frequency in the order of some ten to some hundred MHz, depending on field-strength. TheRF antennae 21 measure the modulated magnetic field M passing through the blood vessel B and anRF reception device 17 at each RF antenna forms a measuring signal or measurement data. The measured signal of eachRF antenna 21 is shown adjacent therespective RF antenna 21. Since there is no flow in the blood vessel B in this figure, the signals are almost identical (here due to the symmetric setup of the RF antennae 21). Again, it should be noted that the generator coil may e.g. also lie between the blood vessel and the RF antennae, since it is not necessary that the blood vessel lies between the generator coil and the RF antennae. -
Figure 5 outlines an example for a possible measurement with a flow. The same setup is used as infigure 4 . In contrast tofigure 4 , there is now blood flowing through the blood vessel B causing the magnetic field to slightly deform in comparison tofigure 4 . Due to this deformation, the measured signals of theRF antennae 21, again shown adjacent therespective RF antenna 21, are different. This difference offers on the one hand a possibility to separate the contribution of the blood flow from contribution of other measurements (that may e.g. form an identical offset in both measurements) and on the other hand a possibility to calculate parameters of the flow itself (e.g. the flux or the periodicity). -
Figure 6 shows an example of a flow-measurement, e.g. recorded with the setup offigure 5 . The amplitude of the measured signals S1, S2 is drawn against the time t in arbitrary units (e.g. mV). The difference between the amplitudes of the two signals S1, S2 results from different energy input in the RF antennae 21 (see e.g. the different field strength infigure 5 at the position of the RF antennae 21). Thus, the output of theRF antennae 21 depends on their position relative to thegenerator coil 20 and the flow direction. - It can be seen that the heartbeat modulates the signals S1, S2 so that the pulse frequency of the blood vessel B can be determined. Furthermore, the signal in the second coil is delayed which can be seen by comparing the two points in time t1, t2 pointing to respective peaks of the blood flow. The delay may e.g. be approximately 120ms. Since the position of the
RF antennae 21 is well-known, this delay can be used to calculate further parameters as e.g. the velocity of the flow. - Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention. For the sake of clarity, it is to be understood that the use of "a" or "an" throughout this application does not exclude a plurality, and "comprising" does not ex-elude other steps or elements. The mention of a "unit" or a "device" does not preclude the use of more than one unit or device.
Claims (15)
- A method for measuring blood flow comprising the following steps:- generating a modulated magnetic field (M) that is a pilot tone signal by a generator coil (20),- recording response signals (S1, S2) of the modulated magnetic field (M) from an object (O) with an RF reception system (7, 21, 17), wherein the response signals (S1, S2) are measured by at least two RF antennae (21) of the RF reception system (7, 21, 17),- separating a flow component of the recorded response signals (S1, S2) from those signal components resulting from movements of the object (O), wherein a flow movement is differentiated from other disturbing influences by a specific frequency and signal profile.
- The method according to claim 1, wherein the generator coil (20) is embedded in a magnetic resonance scanner (2) of a magnetic resonance imaging system (1), preferably near or in an RF reception antenna system (7) of the magnetic resonance scanner (2).
- The method according to one of the preceding claims,
wherein the RF reception system (7, 21, 17) used for recording the response signals of the modulated magnetic field (M) is the RF reception system (7, 17) of a magnetic resonance imaging system, wherein preferably the response signals (S1, S2) of the modulated magnetic field (M) are recorded by RF antennae (21) from the RF reception antenna system (7) of the magnetic resonance scanner (2),
wherein preferably more than three RF antennae (21) are used for measurement. - The method according to one of the preceding claims,
wherein the separation of the flow component of the recorded signals (S1, S2) from those signal components resulting from movements of the object (O), especially from cardiac and respiratory motion, is achieved by using blind and/or semi-blind source separation methods, preferably by using Independent Component Analysis (ICA) or by using a machine learning algorithm trained with ground truth data. - The method according to one of the preceding claims,
wherein the object (O) is arranged between the generator coil (20) and the RF antennae (21), wherein at least the signals from the two RF antennae (21) of the RF reception system positioned closest to a line parallel to the blood flow intended to be measured is recorded. - The method according to one of the preceding claims, wherein a modulation of the modulated magnetic field (M) includes a frequency- within a frequency range which corresponds approximately to the Larmor frequency of the hydrogen atoms of the object in an applied magnetic field (M), preferably within a variance of less than 10 percent deviating from this Larmor frequency
and/or- within a receiving frequency bandwidth of the RF antennae (21) used for the measurement, preferably within a frequency range of less than 10 percent deviating from the Eigenfrequency of these RF antennae (21). - The method according to one of the preceding claims,
wherein after separating the flow component of the recorded signals (S1, S2) from those signal components resulting from movements of the object (O), parameters of the flow are computed, preferably a value of a flux and/or a periodicity. - A system for measuring blood flow comprising:- a first data-interface (22) designed for sending a signal to a generator coil (20), wherein this signal is designed to generate a modulated magnetic field (M) that is a pilot tone signal in the generator coil (20),- a second data-interface (22) designed for recording response signals (S1, S2) of the modulated magnetic field (M) from an object (O) measured with an RF reception system (7, 21, 17), wherein at least the response signals (S1, S2) are measured by two RF antennae (21) of the RF reception system (7, 21, 17),- a separation unit (23) designed to separate a flow component of the recorded response signals (S1, S2) from those signal components resulting from movements of the object, wherein a flow movement is differentiated from other disturbing influences by a specific frequency and signal profile.
- The system according to claim 8, comprising a computing unit (24) designed to compute parameters of the measured flow, preferably a value of a flux and/or a periodicity.
- The system according to claim 8 or 9, comprising a generator coil (20) designed to generate a modulated magnetic field (M), wherein the generator coil (20) is preferably positioned inside a magnetic resonance scanner (2), and/or the system preferably comprises a generator unit (25) for producing the modulation signal for the modulated magnetic field (M) .
- The system according to one of claims 8 to 10, comprising an RF reception system (7, 21, 17) with at least two RF antennae (21) designed to record response signals (S1, S2) of the modulated magnetic field (M) from the object (O), wherein at least the response signals (S1, S2) are measured by the RF antennae (21),
wherein the RF antennae (21) are preferably an RF reception antenna system (5) of a magnetic resonance imaging system (1) . - A control device for controlling a magnetic resonance imaging system comprising a system according to one of claims 8 to 11 and/or designed to perform a method according to any of claims 1 to 7.
- A magnetic resonance imaging system comprising a control device according to claim 12.
- A computer program product comprising a computer program that is directly loadable into a system or a control device for a magnetic resonance imaging system, which comprises program elements for performing the steps of the method according to any of claims 1 to 7 when the computer program is executed by the system or the control device.
- A computer-readable medium on which program elements are stored that can be read and executed by a computer unit in order to perform the steps of the method according to any of claims 1 to 7 when the program elements are executed by the computer unit.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP19176395.2A EP3741293B1 (en) | 2019-05-24 | 2019-05-24 | Method and system for measuring blood flow |
US16/881,243 US20200367765A1 (en) | 2019-05-24 | 2020-05-22 | Method and system for measuring blood flow |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP19176395.2A EP3741293B1 (en) | 2019-05-24 | 2019-05-24 | Method and system for measuring blood flow |
Publications (2)
Publication Number | Publication Date |
---|---|
EP3741293A1 EP3741293A1 (en) | 2020-11-25 |
EP3741293B1 true EP3741293B1 (en) | 2021-06-30 |
Family
ID=66647229
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19176395.2A Active EP3741293B1 (en) | 2019-05-24 | 2019-05-24 | Method and system for measuring blood flow |
Country Status (2)
Country | Link |
---|---|
US (1) | US20200367765A1 (en) |
EP (1) | EP3741293B1 (en) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP3650878A1 (en) * | 2018-11-08 | 2020-05-13 | Siemens Healthcare GmbH | Local coil with integrated pilot tone transmitter |
DE102019208583B4 (en) * | 2019-06-13 | 2023-01-26 | Siemens Healthcare Gmbh | Pilot tone device, magnetic resonance tomograph with pilot tone device and method of operation |
EP3895610B1 (en) * | 2020-04-17 | 2022-11-09 | Siemens Healthcare GmbH | Method and device for detecting movement of a subject in a magnetic resonance imaging device |
WO2023014608A1 (en) * | 2021-08-05 | 2023-02-09 | Arizona Board Of Regents On Behalf Of Arizona State University | System and method for contactless vascular flow measurement |
EP4151148A1 (en) * | 2021-09-17 | 2023-03-22 | UMC Utrecht Holding B.V. | System for determining a physiological parameter of a subject |
Family Cites Families (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040217760A1 (en) * | 2000-02-11 | 2004-11-04 | Madarasz Frank L. | Bayesian methods for flow parameter estimates in magnetic resonance imaging |
US20070088211A1 (en) * | 2003-10-03 | 2007-04-19 | Hu Cheng | Method and apparatus for producing simulated fMRI data |
JP2010522009A (en) * | 2007-03-20 | 2010-07-01 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | Magnetic resonance imaging system and method |
CN101688906B (en) * | 2007-06-19 | 2013-07-17 | 皇家飞利浦电子股份有限公司 | MRI radio frequency receiver |
WO2009088936A1 (en) * | 2008-01-03 | 2009-07-16 | The Government Of The United States Of America, As Represented By The Secretary, Department Of Health And Human Services | Mri guidewire |
CN102860827B (en) * | 2009-09-18 | 2017-05-17 | 东芝医疗***株式会社 | MRI involving arterial spin labeling |
DE102010041659B4 (en) * | 2010-09-29 | 2013-06-13 | Siemens Aktiengesellschaft | Generation of an optimized MR image of an examination object by irradiation of a pulse sequence comprising at least two RF pulses |
US9119550B2 (en) * | 2012-03-30 | 2015-09-01 | Siemens Medical Solutions Usa, Inc. | Magnetic resonance and ultrasound parametric image fusion |
US9788761B2 (en) * | 2014-02-27 | 2017-10-17 | Toshiba Medical Systems Corporation | Motion correction for magnetic resonance angiography (MRA) with 3D radial acquisitions |
US10092199B2 (en) * | 2014-04-01 | 2018-10-09 | Siemens Healthcare Gmbh | MR imaging apparatus and method for generating a perfusion image with motion correction |
DE102015203385B4 (en) | 2015-02-25 | 2017-11-30 | Siemens Healthcare Gmbh | Method for generating motion information to an at least partially moving examination area and magnetic resonance system and hybrid imaging modality |
DE102015224162B4 (en) * | 2015-12-03 | 2017-11-30 | Siemens Healthcare Gmbh | Method for determining a movement information and a magnetic resonance device describing a movement in an at least partially moved examination area |
DE102015224158A1 (en) | 2015-12-03 | 2017-06-08 | Siemens Healthcare Gmbh | Signal transmitter for pilot tone navigation |
JP6547612B2 (en) * | 2015-12-14 | 2019-07-24 | コニカミノルタ株式会社 | IMAGE PROCESSING APPARATUS, IMAGE PROCESSING METHOD, AND ULTRASONIC DIAGNOSTIC APPARATUS PROVIDED WITH IMAGE PROCESSING APPARATUS |
EP3413076B1 (en) * | 2017-06-08 | 2022-01-26 | Siemens Healthcare GmbH | Mri involving the generation of a physiological motion signal using a pilot tone navigator |
US11026636B2 (en) * | 2017-06-08 | 2021-06-08 | Siemens Healthcare Gmbh | Method for generating a medical data set of a moving body part |
EP3486672A1 (en) * | 2017-11-16 | 2019-05-22 | Koninklijke Philips N.V. | Magnetic resonance imaging system with rf motion detection |
-
2019
- 2019-05-24 EP EP19176395.2A patent/EP3741293B1/en active Active
-
2020
- 2020-05-22 US US16/881,243 patent/US20200367765A1/en active Pending
Non-Patent Citations (1)
Title |
---|
None * |
Also Published As
Publication number | Publication date |
---|---|
US20200367765A1 (en) | 2020-11-26 |
EP3741293A1 (en) | 2020-11-25 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP3741293B1 (en) | Method and system for measuring blood flow | |
US8183864B2 (en) | System for multi nucleus cardiac MR imaging and spectroscopy | |
US9301704B2 (en) | Magnetic resonance imaging system for non-contrast MRA and magnetic resonance signal acquisition method employed by the same | |
US9305376B2 (en) | Magnetic resonance imaging apparatus and method of acquiring functional image | |
CN111480089B (en) | Magnetic resonance imaging system with motion detection | |
US20100106008A1 (en) | Magnetic resonance imaging system and method | |
JP5074211B2 (en) | Magnetic resonance imaging system | |
US20030036693A1 (en) | Method to obtain the cardiac gating signal using a cardiac displacement sensor | |
CN101636664A (en) | Magnetic resonance imaging system and method | |
US11071469B2 (en) | Magnetic resonance method and apparatus for determining a characteristic of an organ | |
US8185187B2 (en) | Magnetic resonance lmethod and apparatus with gated shimming of the basic magnetic field | |
EP3349030A1 (en) | Magnetic resonance imaging apparatus and controlling method therefor | |
US20170131377A1 (en) | Magnetic resonance imaging apparatus and method | |
US20040186372A1 (en) | Mr method for the examination of a cyclically changing object | |
US20220361822A1 (en) | Method and system for detecting movement of at least one part of a subject | |
KR101541290B1 (en) | Method and apparatus for measuring magnetic resonance signals | |
US6759848B2 (en) | Magnetic resonance method and apparatus for spatially resolved presentation of change in the functional activities of a brain | |
US8410778B2 (en) | Magnetic resonance method and apparatus to acquire multiple image data sets from a subject | |
US20190328265A1 (en) | Magnetic resonance image display device and magnetic resonance image display method | |
KR102092908B1 (en) | Magnetic Resonance Imaging Apparatus for Correcting Respiratory Movement | |
JP2008148918A (en) | Mri system and its control method | |
KR20170087673A (en) | Magnetic resonance imaging apparatus and method for shimming of magnetic resonance imaging apparatus thereof | |
US20180011160A1 (en) | Reduction of eddy currents during flow encoded magnetic resonance imaging | |
EP4382945A1 (en) | Magnetic resonance imaging system | |
KR102257963B1 (en) | Apparatus for Detecting Respiratory Interval Using Histogram Cumulative Distribution of Respiratory Gating Signal |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: REQUEST FOR EXAMINATION WAS MADE |
|
17P | Request for examination filed |
Effective date: 20200120 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
AX | Request for extension of the european patent |
Extension state: BA ME |
|
GRAP | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOSNIGR1 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: GRANT OF PATENT IS INTENDED |
|
RIC1 | Information provided on ipc code assigned before grant |
Ipc: G01R 33/56 20060101ALI20201130BHEP Ipc: A61B 5/026 20060101AFI20201130BHEP Ipc: A61B 5/055 20060101ALN20201130BHEP Ipc: G01R 33/565 20060101ALN20201130BHEP Ipc: A61B 5/113 20060101ALN20201130BHEP |
|
INTG | Intention to grant announced |
Effective date: 20201221 |
|
GRAS | Grant fee paid |
Free format text: ORIGINAL CODE: EPIDOSNIGR3 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE PATENT HAS BEEN GRANTED |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: EP |
|
REG | Reference to a national code |
Ref country code: AT Ref legal event code: REF Ref document number: 1405583 Country of ref document: AT Kind code of ref document: T Effective date: 20210715 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R096 Ref document number: 602019005690 Country of ref document: DE |
|
REG | Reference to a national code |
Ref country code: IE Ref legal event code: FG4D |
|
REG | Reference to a national code |
Ref country code: LT Ref legal event code: MG9D |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: BG Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210930 Ref country code: FI Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: HR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 |
|
REG | Reference to a national code |
Ref country code: NL Ref legal event code: MP Effective date: 20210630 |
|
REG | Reference to a national code |
Ref country code: AT Ref legal event code: MK05 Ref document number: 1405583 Country of ref document: AT Kind code of ref document: T Effective date: 20210630 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20211001 Ref country code: LV Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: NO Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210930 Ref country code: SE Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: RS Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: EE Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: ES Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: SM Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: PT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20211102 Ref country code: RO Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: NL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: AT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: CZ Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: PL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R097 Ref document number: 602019005690 Country of ref document: DE |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: AL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 |
|
26N | No opposition filed |
Effective date: 20220331 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: PL |
|
REG | Reference to a national code |
Ref country code: BE Ref legal event code: MM Effective date: 20220531 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: MC Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: LU Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20220524 Ref country code: LI Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20220531 Ref country code: CH Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20220531 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: LT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: IE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20220524 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: BE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20220531 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20230515 Year of fee payment: 5 Ref country code: DE Payment date: 20220620 Year of fee payment: 5 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R081 Ref document number: 602019005690 Country of ref document: DE Owner name: SIEMENS HEALTHINEERS AG, DE Free format text: FORMER OWNER: SIEMENS HEALTHCARE GMBH, MUENCHEN, DE |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: MK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 Ref country code: CY Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20210630 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: HU Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT; INVALID AB INITIO Effective date: 20190524 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 20240603 Year of fee payment: 6 |